The Omen window will only display while you are in combat. It has no meaning when you are out of combat as there is no such thing as threat. Select the "Omen" mode in the information panel and enter combat. If you have Recount installed, the Recount window will vanish and the Omen window will display.

You should also see the threat bar in your HUD after you enter combat.

OK thanks, I seem to have it working now. I engaged in combat previously but I must have not had Omen selected in the information panel, or something. Still, it is rather hard to configure any Omen settings when it's impossible to make the window appear to even see test bars unless you are in combat. The Recount window doesn't behave this way, and is visible for configuration any time, whereas when I click the information bubble to go from "Stats" (Recount) to "Omen", nothing happens and the Recount window remains. Why not make the Omen window blank, but visible, at any time?